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Hands Free CFD

When a person describes their ideal design software, or any software for that matter, Ease-of-Use is always on the list of desirable attributes. It makes sense that in order to be productive with the software in the shortest amount of time the software must be easy to use. All of the CAD and CFD tools I work with strive to achieve this goal (except for one which I won’t name and it isn’t one of our products) and hit the mark most of the time. For me, when considering CFD tools for the design engineer, the Ease-Of-Use concept extends from the start of the conceptual design through to the report that gets the final design approved. Factors that are important are:

Speed of manual geometry creation

Ability to integrate existing MCAD and ECAD data

Ability to export MCAD and ECAD data

Speed and robustness of mesh and solver

Ability to review results to steer the design

Ability to share results to convince management

For PCB analysis we have taken Ease-Of-Use to a new level, a level where you don’t even need to open the software. From a command line you can feed the solver an IDF file of the PCB (or even better, our FloEDA file) and link it to a thermal parts library to replace the critical components with a proper thermal representation. The mesh and solve are handled automatically and when the run is complete, say 15 minutes later, an html report is created. The report lists which components are running too hot and even provides pretty pictures of surface temperatures. For me, this is an evolutionary step with CFD. While I can truly appreciate all of the meshing, conservation equations, and sophisticated numerical schemes to reach conservation, I don’t always need to see it.

PCB thermal analysis lends itself to this sort of Hands Free approach, at least in the preliminary stages, because of the analysis environment and the desired output. In the early stages of a PCB thermal design it is either going to be considered in natural convection or have some air forced over it. The desired output is the junction temperature, it’s always about the junction temperature.

Their is another industry that could benefit from the same type of automation, at least in the early design phases, and that is Data Centers. At the early stages, it is a room laid out on a 2’x2′ grid with Racks, CRACS, and floor tiles. Artistic representation below:

It seems to me that there could be a standard similar to IDF, that lays out the room. In fact, maybe the same standard could be used. This could be linked to a library that replaces the place holders with a proper thermal and airflow definition. The output is well understood, at least in my mind. What are the Rack inlet temperatures? What are the floor tile flow rates? What is the cooling load on each CRAC. And give me a few contour plots to show the managers.

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About John Wilson

John Wilson joined Mentor Graphics Corporation, Mechanical Analysis Division (formerly Flomerics Ltd) in 1999. John has worked on or managed more than 100 thermal and airflow design projects. His modeling and design knowledge range from Electronics Cooling IC packaging level to Data Centers and Clean Rooms. He has extensive experience in IC package level test and analysis correlation through his work at Mentor Graphics' San Jose based Thermal Test Facility. He is currently the Consulting Engineering Manager, WRO in the Mechanical Analysis Division.
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